Jim Al-Khalili is deeply concerned that people believe "we can slash our reliance on coal and gas solely through renewable resources, such as wind and solar, along with energy conservation" (Nuclear waste is hardly a worry when the climate change threat is so urgent, July 26).

I own up to being a believer and, as a fellow physicist, ask: where is Jim's data? Here is some of mine. More solar energy strikes the Earth in one hour than is consumed by all human activity in a year. In the UK more than 60% of our electricity is used in buildings. The solar energy falling on those buildings exceeds by more than seven times the energy consumed inside.

Hence more than half the UK electricity demand could be met by covering all south-facing roofs with the current 14%-efficient solar photovoltaic (PV) panels. That is ignoring small wind turbines and new technology. The PV cells my company is commercialising have twice this efficiency and can be much less obtrusive.

The most significant feature of the newer wind turbine and PV systems is that they come in small units and can be installed very quickly. Not only do these micro-generation technologies have much shorter lead-in times than the 10-year wait for nuclear stations (or the 20-35 years for Al-Khalili's technology to transmute nuclear waste), but installations can grow exponentially, as happens for consumer electrical products. The most optimistic assumption for new nuclear build is a linear rise of one new reactor a year, starting in 10 years' time.

For example, PV use in Germany has been growing exponentially over the past decade. One hundred times as much PV electrical capacity as in the UK has already been installed. If similar policies were introduced here, the combination of wind and PV electricity generation would dwarf the proposed nuclear build well before a single new nuclear unit of electricity is generated.

According to Al-Khalili, people like me are "utterly irrational" in being concerned about nuclear waste. But plutonium will be a problem for hundreds of thousands of years, not tens of thousands as he claims.

He argues that science will eventually find a way "to deal with this buried waste thousands of years in the future". I consider it immoral that we should leave more than 10,000 generations to deal with the waste of the three generations who will have consumed the world's exploitable uranium reserves. For a start, how will they know where the plutonium is buried, when the store must survive intact for more than 100 times the age of Stonehenge?

Rather than developing transmutation or fast-breeder schemes which may not work, and which involve the transportation of large amounts of plutonium, the highest priority of the nuclear industry should be to solve the long-term waste storage problem. The urgency of finding a solution was re-emphasised by the recent revelation that the failed London tube bombers had the plans of the Sizewell B nuclear station.

· Keith Barnham is emeritus professor of physics at Imperial College London, and a co-founder of the solar cell manufacturing company QuantaSol